Multiple media content, including for example, textual, graphical or pictorial, video, and audio information items and combinations thereof, can be viewed interactively by a user with computer applications referred to herein as multiple media viewers. In addition to displaying, playing or otherwise presenting various related media, these multiple media viewers generally provide tools for the user to browse and search through information presented in the multiple media content.
In prior art multiple media viewers, the multiple media content typically is stored on a CD-ROM which is inserted into a CD-ROM drive on the user's computer for access by the viewer. Examples include, among others, Microsoft Corporation's Multimedia Viewer version 2.0 multiple media viewer, and Microsoft Corporation's Encarta.RTM., Cinemania.RTM., Dinosaurs.RTM., and Baseball 1995.RTM. CD-ROM multiple media titles (which incorporate a CD-ROM based multiple media viewer). The CD-ROM generally provides sufficient storage for a single multiple media title. More importantly, the transmission bandwidth of current CD-ROM drives is sufficient to provide near instantaneous or on-demand rendering of the multiple media content responsive to user input.
Some prior art multiple media viewers connect via a modem and telephone line (or wireless telephone service) to an on-line service provider to access multiple media content which is resident on a remote central computer (hereafter "server"). Examples include the front-end or user applications for the major on-line service providers such as Compuserve, America On-Line, and Prodigy, as well as Mosaic and other internet world-wide-web browsers. Such on-line delivery of multiple media content has the advantage of potentially lowering the cost of distribution of the information (e.g., by avoiding the costs of reproducing, distributing, and retailing CD-ROMs for multiple media titles). Further, the on-line service provider can provide access for its subscribers to a large number (e.g., hundreds or even thousands) of multiple media titles.
The drawback to on-line multiple media viewers is that the modem connection to the on-line service provider has a much lower data transmission rate (on the order of 1 KByte/s for a 9600 baud/s modem) compared to CD-ROM drives (typical quad-speed CD-ROM drives have a data transfer rate of about 600 Kbyte/s). Even further, modem connections to an on-line service provider suffer long latencies (e.g., 0.5-2 seconds is common) between an initial request for data and its reception due to multiple layers of transmission protocols for packetizing and routing data through the on-line service provider's network and for signal propagation between the client and server. This results in a long delay between a request initiated by a user input for a particular media item (e.g., a text, image, or sound) in a multiple media title at the server, and the availability of the media item for rendering by the viewer application at the user's computer.
In general, prior on-line multiple media viewers are client-driven. The on-line multiple media viewer application running on the user's computer (referred to as the "client") controls all data transfers from the server. Typically, each media item is requested synchronously as a separate file download by the client viewer. The client viewer waits for each requested media item transfer to complete before requesting a subsequent media item. Prior on-line multiple media viewers may perform several of these synchronous transfers before rendering any part of a presentation involving multiple media items. Consequently, rendering of the presentation may be delayed by the latency of several transfer requests and the duration of several file transfers after the user's activating input. Where graphical or pictorial, video, or audio media items are involved, the delay before rendering of a presentation or even parts thereof can be tens of seconds or minutes. Prior on-line multiple media viewers therefore have lacked sufficient speed and responsiveness for effective interactive viewing and browsing of multiple media content.
A purpose of the invention therefore is to enable the viewing of multiple media titles over on-line connections with a remote server, including current slow on-line connections.